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Including postcompensation

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398 - Optical communications

398202000 - RECEIVER

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Class / Patent application numberDescriptionNumber of patent applications / Date published
398210000 Amplitude 11
398209000 Feedback 11
398211000 Intermodulation 2
20110038642TECHNIQUE FOR DETECTION OF OPTICAL DATA SIGNALS - Technology for detecting an optical data signal carried in a combined optical signal that comprises a carrier optical signal modulated by the optical data signal and also comprises ASE noise. The proposed optical data detector/receiver is provided with an SHG device adapted to generate a second harmonic optical signal of the carrier optical signal modulated by the data signal. In the signal, generated by the SHG, the ASE noise will be essentially reduced.02-17-2011
20100232811Highly Tunable, Low Jitter Optical Clock Generation - An apparatus is disclosed for the optical generation of clock signals with tunable frequency and low jitter. A laser source serves as both the carrier used to transmit the clock signal for use by other optical, electronic or hybrid circuit elements and the original modulation time base. A fraction of the original laser source undergoes one or more stages of frequency division before being recombined as a modulation signal with the remaining laser beam. Transmission of the resulting signal via single mode fiber and dividers retains the low jitter properties of the modulated signal. By starting with a clock signal of optical frequency then dividing downward in frequency, comparatively high frequency clocks may be generated, notably in the GigaHertz and TeraHertz frequency ranges.09-16-2010
Entries
DocumentTitleDate
20120177386ELECTRONIC PHASE CONJUGATION FOR IMPAIRMENT COMPENSATION IN A FIBER COMMUNICATION SYSTEM - Exemplary embodiments include a method and systems for impairment compensation in a communication system. The systems can include an electronic phase conjugation system that receives an incoming optical signal from a first section of a fiber optic link, converts the incoming optical signal to an in-phase electric signal and a quadrature electrical signal, and generates a phase conjugated outgoing optical signal from the in-phase and quadrature electrical signals. The phase conjugated outgoing optical signal compensates for impairment of the fiber in the communication system.07-12-2012
20100074632Method for improving the performance of digital coherent optical receiver using single ended photo-detection - A method and system for mitigating distortion in coherent single-ended photo-detection is disclosed. The methodology comprises: receiving an optical signal carried on an optical transmission medium and coherently detecting the received optical signal to produce a digitized signal; estimating a time-dependent random variable introducing distortion to the coherently detected signal; and subtracting the distortion from digitized signal to produce a distortion mitigated output signal.03-25-2010
20100111545MULTISCALE SAMPLING FOR WIDE DYNAMIC RANGE ELECTRO-OPTIC RECEIVERS - A method for multiscale sampling for wide dynamic range electro-optic receivers is presented. The method comprises obtaining a signal, reproducing the signal into first and second signals, scaling one signal with respect to the other, modulating both signals with the same modulation function, and utilizing the resulting vector response function to invert the response of the link over a greater dynamic range than would otherwise be possible with a single instance of the modulated signal. The sealed modulation response may be obtained by splitting the signal into two polarizations and utilizing a modulator having different response for the two polarizations, or by utilizing two modulators.05-06-2010
20090154941SYSTEMS AND METHODS FOR COMMUNICATION SYSTEM CONTROL UTILIZING CORRECTED FORWARD ERROR CORRECTION ERROR LOCATION IDENTIFIERS - The present invention provides systems and methods for communication system control utilizing corrected forward error correction (FEC) error location identifiers in multi-level modulation scheme systems. The present invention utilizes precise error correction information, available for each FEC block of a particular code (including, but not limited to, block codes and concatenated block codes employing iterative decoding as well as convolutional codes (including turbo codes) and low-density parity-check code (LDPC) class codes) used (e.g., Bose, Ray-Chaudhuri, Hocquenghem (BCH), Reed-Solomon, etc.), as a result of the FEC decoding process to provide feedback to close the loop for control of a demodulator (i.e., receiver). Each error location can be uniquely traced back to a particular sub-rate signal path, with running, post-FEC corrected BER (bit error rate) calculations generated on each sub-rate signal. Advantageously, this provides the ability to adjust thresholds and various other parameters to achieve and maintain error-free operation quickly.06-18-2009
20100040383Differential multilevel modulated optical signal receiver apparatus - A first optical splitter splits an input optical signal and outputs it to first and second optical paths. A second optical splitter outputs the optical signal from the first optical path to third and fourth optical paths. A third optical splitter outputs the optical signal from the second optical path to fifth and sixth optical paths. In the second optical path, 1-symbol delay element and π/4 phase shifter element are configured. In the fourth optical path, π/2 phase shifter element is configured. First and second adjuster circuits adjust the optical path length of the second and the fourth optical paths, respectively, by temperature control. A first optical coupler couples optical signals transmitted via the third and the fifth optical paths. A second optical coupler couples optical signals transmitted via the fourth and the sixth optical paths. Photodetectors convert the optical signals from the optical couplers into electrical signals.02-18-2010
20090129788Optical Receiver For Receiving A Signal With M-Valued Quadrature Amplitude Modulation With Differential Phase Coding And Application Of Same - Optical data signal receiver having an optical separation of the received data signal into two signal paths, namely, an amplitude detection path and a phase detection path, wherein the phase detection path is split into an in-phase signal path generating in-phase-signals and a quadrature-signal path generating quadrature-signals, and both the in-phase-signal path and the quadrature-signal path, as well as the amplitude detection path, are connected to an analysis unit for demodulation of the received data signal, in which a normalizer and thereafter a symbol discriminator and a data reconstruction logic are arranged in the analysis unit. In the receiver, a connection is provided at least from the amplitude detection path to the normalizer, the normalizer normalizing the in-phase and quadrature-signals with the aid of the signal output from the amplitude detection path, the symbol discriminator discriminating the symbols output from the normalized in-phase and quadrature-signals. Additional connections can be provided from the amplitude detection path signal.05-21-2009
20130045015METHOD AND ARRANGEMENT FOR SIGNAL PROCESSING IN A COMMUNICATION SYSTEM - A signal processing method and a signal processing arrangement for coherent receivers are provided. The method includes the steps of receiving a coherent complex signal, extracting orthogonal in-phase and quadrature signal components from the coherent complex signal, quantizing the orthogonal signal components independently, combining the quantized orthogonal signal components as real and imaginary part of a complex number resulting in a first signal, and soft differential decoding the first signal resulting in a second signal.02-21-2013
20130084080COHERENT OPTICAL RECEIVER AND COHERENT OPTICAL RECEIVING METHOD - A coherent optical receiver according to an exemplary aspect of the present invention includes a coherent optical receiving unit, a first waveform equalizing circuit compensating waveform distortion caused by characteristics of the coherent optical receiving unit and compensating chromatic dispersion in a predetermined range to an input signal, a second waveform equalizing circuit compensating chromatic dispersion of the input signal, and a controller monitoring a chromatic dispersion amount of the input signal and controlling a compensation coefficient regarding the chromatic dispersion compensation performed by each of the first waveform equalizing circuit and the second waveform equalizing circuit depending on the chromatic dispersion amount to be compensated. 04-04-2013
20100092186OPTICAL RECEIVER AND LIGHT RECEIVING METHOD - An apparatus and method includes converting an optical signal that is received into an electrical signal and outputting the electrical signal, converting the electrical signal into a data signal and outputting the data signal by comparing the electrical signal with a reference voltage, monitoring the electrical signal and output monitored information, and controlling the reference voltage based on the monitored information.04-15-2010
20130089342MINIMUM VARIANCE CARRIER RECOVERY WITH INCREASED PHASE NOISE TOLERANCE - A method of data symbol recovery. An optical signal is modulated by a transmitter using a modulation scheme comprising a symbol constellation having a predetermined asymmetry and detected at a receiver. Phase error estimates corresponding to data symbol estimates detected from the received optical signal are calculated. A phase rotation is calculated based on the phase error estimates, using a filter function, and the phase rotation applied to at least one data symbol estimate to generate a corresponding rotated symbol estimate. The phase error estimates model the asymmetry of the symbol constellation, such that the computed phase rotation can compensate phase noise that is greater than one decision region of the symbol constellation.04-11-2013
20130089341MINIMUM VARIANCE CARRIER RECOVERY - Accordingly, an aspect of the present invention provides a method of data symbol recovery. A respective probabilistic phase error is calculated for each of a plurality of data symbol estimates. A phase rotation is calculated based on the probabilistic phase error estimates, using a filter function, and the phase rotation applied to at least one data symbol estimate to generate a corresponding rotated symbol estimate. Each rotated symbol estimate is processed to generate corresponding decision values of each data symbol.04-11-2013
20090317093DPSK OPTICAL RECEIVER - A DPSK optical receiver includes a DPSK demodulation circuit, an optical bandpass filter, a first photodetector, and a first control circuit. The DPSK demodulation circuit demodulates a DPSK optical signal and outputs the DPSK demodulated optical signal. The optical bandpass filter extracts a demodulated optical signal near the center wavelength from the DPSK demodulated optical signal output from the DPSK demodulation circuit. The first photodetector detects the optical power level of the DPSK demodulated optical signal extracted by the optical bandpass filter. The first control circuit performs phase control on the DPSK demodulation circuit so as to optimize the DPSK demodulation circuit with respect to the center wavelength of the DPSK optical signal on the basis of the optical power level detected by the first photodetector.12-24-2009
20090116852OPTICAL RECEIVER IMPLEMENTED WITH DUAL ELECTRONIC DISPERSION COMPENSATORS - An optical receiver implemented with two electronic dispersion compensators (EDC) is disclosed. The optical receiver selects one of the EDC in an ordinary operation. Once there shaped signal compensated by the selected EDC is degraded due to irregular conditions of the optical transmission line, the optical transmitter and so on, the optical receiver reconfigures the tap coefficients of the unselected EDC and switches to the newly configured EDC after setting the tap coefficients for the new condition of the transmission line and the transmitter.05-07-2009
20120219303Efficient Computation And Compensation Of Linear And Nonlinear Distortion In Dispersion-Managed Fiber-Opic Transmission - In one embodiment, a method for performing nonlinearity compensation on a dispersion-managed optical signal that was transmitted over an optical communication link, the method including virtually dividing the communication link into a plurality of steps, performing lumped dispersion compensation on a received optical signal to obtain a waveform upon which digital backward propagation (DBP) can be performed, performing DBP by performing dispersion compensation and nonlinearity compensation for each step, and generating an estimate of the transmitted signal based upon the performed DBP.08-30-2012
20120219302PMD AND CHROMATIC DISPERSION TOLERANT CLOCK RECOVERY - Consistent with the present disclosure, a method and system for detecting a clock phase of an optical signal in a coherent receiver is provided that is insensitive to polarization mode dispersion (PMD) and other polarization effects in the optical communication system. The clock phase of the received signal is estimated by first calculating a phase shift between a pair of related frequency domain data outputs of a Fourier transform circuit. The calculated phase shift includes a phase component and a data spectrum component. The calculated phase shift is then averaged over a number of clock cycles to remove the data spectrum components thus enabling extraction of the phase component. A determinant function on the time averaged result is used to normalize any effects of PMD from the received signal and isolate the phase component. In this manner, the phase component is not dependent on the PMD effects in the optical communication system. The imaginary part of the phase component is then calculated to estimate the clock phase error which is used to tune an oscillator in the receiver to synchronize a sampling phase in the receiver with the received signal. An estimated value for the chromatic dispersion is determined from a resultant value of the determinant function and used to compensate for the effects of chromatic dispersion from the clock phase error estimate.08-30-2012
20090238582Optical receiver - In an optical receiver, a light receiving element receives the optical packet signals and converts the optical packet signals to electrical signals. A bias voltage supply section supplies bias voltage to the light receiving element. A monitoring section monitors an input level of each optical packet signal or each electrical signal and transmits a monitored value to the bias voltage supply section. In addition, the bias voltage supply section temporarily increases the bias voltage according to magnitude of the monitored value after an end of receiving of each optical packet signal.09-24-2009
20120114341SYSTEM AND METHOD FOR FREQUENCY-DOMAIN CHROMATIC DISPERSION AND POLARIZATION MODE DISPERSION COMPENSATION WITH TIME-DOMAIN CHANNEL ESTIMATION - A system and method are disclosed which compensate for chromatic dispersion and polarization mode dispersion in a digital signal. The signal is adjusted for chromatic dispersion in the frequency-domain. The signal is then converted to the time-domain and at least a portion of the signal is estimated to produce channel parameters. The channel parameters are converted to the frequency domain and used to compensate for polarization mode dispersion in the signal.05-10-2012
20080212982OPTICAL RECEIVER, OPTICAL RECEIVING APPARATUS USING THE OPTICAL RECEIVER AND OPTICAL RECEIVING METHOD THEREOF - An optical receiver includes an optical amplifier configured to amplify an input optical signal and output an amplified optical signal; and a light receiving element configured to convert the amplified optical signal into an electrical signal and output the electrical signal, and the optical amplifier controls an output-level of the amplified optical signal according to a wavelength of the input optical signal.09-04-2008
20090279901PASSIVE COMPONENT FOR ALL-OPTICAL REGENERATION OF HIGH LEVELS BY SATURABLE ABSORPTIONS CAVITY - An optical component for processing an optical signal, operating by reflection in a saturable absorption resonant cavity formed between a first so-called rear mirror and a second mirror situated on the side of the incident signal, the reflectivity of the second mirror being greater than or equal to the reflectivity of the rear mirror.11-12-2009
20100284702Optical Receivers with Controllable Transfer Function Bandwidth and Gain Imbalance - Techniques, devices and systems based on optical receivers with controllable transfer function bandwidth and gain imbalance.11-11-2010
20090285585Method and apparatus for polarization stabilization in optical receivers with complex modulation formats - High optical communication rates are making their way into networks initially designed for 10 Gigabits per seconds (Gbps). These higher rates of 40 Gbps and higher have shorter signaling periods and are more susceptible to differential group delay (DGD). A method and corresponding apparatus in an example embodiment of the present invention compensates for polarization state sensitivity of a receiver by determining a performance metric relating to an error rate due to transmission and reception of a modulated optical signal in a medium introducing DGD. Based on the performance metric, a control vector is determined to control a polarization state of the modulated optical signal. The control vector is applied to a polarization effecting device to compensate for the DGD and the polarization state sensitivity of the receiver. Communication rates of 40 Gbps and higher can be used in transmission mediums that introduce DGD through use of embodiments presented.11-19-2009
20100119241ADAPTIVE FREQUENCY DOMAIN EQUALIZATION WITHOUT CYCLIC PREFIXES - Polarization multiplexing, optical communications systems can suffer from chromatic dispersion and polarization mode dispersion, resulting in channel delay spread. These errors can be compensated quickly and simply in the frequency domain. By obviating the need for a cyclic prefix, the complexity of the equalization can be reduced by more than a factor of twenty.05-13-2010
20110200339OPTICAL RECEIVER - An optical receiver includes: a waveform distortion compensator to perform an operation on digital signal representing an optical signal generated by an A/D converter to compensate for waveform distortion of the optical signal; a phase detector to generate phase information representing sampling phase of the A/D converter; a phase adjuster to generate digital signal representing an optical signal in which the sampling phase of the A/D converter is adjusted from an output signal of the waveform distortion compensator using the phase information; a demodulator to generate a demodulated signal from the output signal of the phase adjuster; a phase controller to control the sampling phase of the A/D converter; a peak detector to detect a peak value of the phase information while the sampling phase of the A/D converter is controlled by the phase controller; and a compensation controller to control the waveform distortion compensator using the peak value.08-18-2011
20090142076Frequency offset compensating apparatus and method, and optical coherent receiver - The present invention relates to a frequency offset compensating apparatus and method, and an optical coherent receiver. The optical coherent receiver includes a front end processor and a frequency offset estimator, of which said front end processor converts an inputted optical signal into a base band digital electric signal, and said frequency offset estimator estimates a phase offset change introduced by a frequency offset in said base band digital electric signal; said frequency offset compensating apparatus comprises an M output integrator, for integrating the phase offset change introduced by the frequency offset to acquire M inverse numbers of the phase offset introduced by the frequency offset, where M is an integer greater than 1; a series-parallel converting device, for dividing said base band digital electric signal into M sub base band digital electric signals; M complex multipliers, for constructing the corresponding inverse numbers in the M inverse numbers to be complex numbers, and multiplying them with the corresponding sub base band digital electric signals in the M sub base band digital electric signals; and a parallel-series converting device, for converting the M sub base band digital electric signals multiplied by said complex multipliers into a base band electric signal.06-04-2009
20100098439OPTICAL SIGNAL CONCENTRATOR AND OPTICAL RECEIVER USING THE SAME - Disclosed are an optical signal concentrator and an optical receiver for wireless optical communication. The concentrator includes a diffusion sheet and a light guide plate positioned below the diffusion sheet for guiding diffused optical signals perpendicularly to the incident direction the diffused optical signals, the light guide plate being formed with at least one concentric circle pattern facing the diffusion sheet. The receiver includes an optical signal concentrator including a diffusion sheet, a light guide plate positioned below the diffusion sheet for guiding the optical signals perpendicularly to the incident direction the diffused optical signals, one or more optical detectors for detecting light projected to the side of the light guide plate, and a reflection plate for reflecting light incident to the light guide plate.04-22-2010
20120106983OPTIMIZED NORMALIZED LEAST MEAN SQUARE PHASE ESTIMATION - Methods and systems for normalized least mean square phase estimation are shown that include receiving optical transmissions that include a modulated signal, determining a step size based on a signal-to-noise ratio (SNR) and a laser linewidth that provides a balance between convergence speed and precision, estimating phase error using the determined step size, derotating the modulated signal to remove the estimated phase error, and demodulating the derotated signal to produce a bitstream.05-03-2012
20120106982Coherent optical receiver with adaptive equalizer initialization system - An adaptive-equalizer initialization system performs three functions: frequency offset estimation, taps estimation for chromatic dispersion filters, and taps initialization for an adaptive equalizer. The system contains hardware FFT and peak detector units that sense a pure tone that marks the beginning of a known, short data sequence.05-03-2012
20090279902METHOD AND APPARATUS FOR DEMODULATING AND REGENERATING PHASE MODULATED OPTICAL SIGNALS - A DPSK/DQPSK receiver includes an optical splitter that separates the received DPSK/DQPSK optical signal according to an optical power splitting ratio into a plurality of received optical signals. A plurality of optical filters passes a plurality of filtered received optical signals. A plurality of optical detectors generates a plurality of electrical detection signals, each with a power that is related to a power of a respective filtered optical signal. A plurality of amplifiers generates a plurality of amplified electrical signals. At least one electrical signal combiner combines the plurality of amplified electrical detection signals generated by the plurality of optical amplifiers into a combined reception signal.11-12-2009
20090297169Optical signal receiving apparatus and optical signal attenuation controlling method - A VOA maximum attenuation control circuit has, in addition to a conventional VOA maximum attenuation control circuit, a first resistor and a second resistor, a transistor which is an emitter follower type PNP transistor, and a capacitor. Since charge of the capacitor is 0 volt at the instant when power of the optical interface unit or each optical interface is shifted from OFF state to ON state, current is supplied to a VOA by the transistor in association with shift to the ON state of the power. As a result, attenuation of the VOA reaches maximum. When the capacitor is gradually charged, base potential of the transistor is finally +5 volts, and current is 0 ampere. Then shifting to maximum attenuation control of the VOA by an operational amplifier is realized.12-03-2009
20110206386Apparatus and Method for Stabilizing Power to an Optical Multimode Receiver - To stabilize power to an optical multimode receiver a multimode variable optical attenuator is connected to the receiver with the attenuator's voltage being controlled using a feedback signal provided by an output detector, the signal being processed using a control algorithm based on proportional-integrate-differential theory.08-25-2011
20120294630Blind Carrier Frequency Offset Detection for Coherent Receivers Using Quadrature Amplitude Modulation Formats - Exemplary embodiments are directed to a blind carrier recovery system for blind detection and/or correction of carrier frequency offset between the signal laser source and local oscillator (i.e., carrier frequency recovery) for optical systems employing quadrature amplitude modulation (QAM). Exemplary embodiments can be implemented using an improved fast Fourier transform (FFT)-based approach. Some embodiments can include a frequency sign detection technique that uses parallel, concurrently implemented FFTs having a modified FFT architecture. Some embodiments can include a frequency sign detection technique that uses time-domain slope detection based on constellation classification.11-22-2012
20110268459TIMING RECOVERY IN PRESENCE OF OPTICAL IMPAIRMENTS AND OPTIMIZATION OF EQUALIZATION BASED ON TIMING RECOVERY MOMENT STRENGTHS - The present disclosure provides timing recovery in optical systems in the presence of chromatic dispersion (CD), polarization mode dispersion (PMD), and polarization dependent loss (PDL) and to optimization of equalization settings based upon timing recovery moment strengths. A stable timing point may be determined in the presence of PMD and PDL impairments, even when the direct estimate of timing becomes unreliable. This determination may be performed entirely in the digital domain providing precise, predictable performance. Also, the present invention utilizes a monotonic relationship between the timing metric and CD setting error to provide directed search in setting the CD equalizer thereby reducing significantly the overall search effort in optimizing CD equalizer settings. This utilizes computations already performed by the transceiver for timing recovery function yielding a computational advantage over competing methods.11-03-2011
20100135677Temperature Controlled Interferometer For Phase Demodulation - An interferometer includes an optical beam splitter that splits an input optical signal into a first optical signal propagating in a first optical path comprising free space and a second optical signal propagating in a second optical path comprising a dielectric medium. A differential delay delays the second optical signal relative to the first optical signal by a differential delay time that is proportional to at least one of a temperature and a refractive index of the dielectric medium. A temperature controller in thermal contact with the dielectric medium changes the temperature of the dielectric medium to control at least one of thermal expansion/contraction and a temperature dependent change in the refractive index of the dielectric medium, thereby changing the differential phase delay. An optical beam splitter/combiner optically coupled to the first and second optical paths generates a first and second interferometric optical signal having an amplitude and phase that is related to the differential delay.06-03-2010
20090129787Optical coherent receiver, frequency offset estimating apparatus and method for optical coherent receiver - The present invention discloses an optical coherent receiver, and a frequency offset estimating apparatus and a frequency offset estimating method for use in the optical coherent receiver. The optical coherent receiver includes a front end processing section for changing an optical signal into a base band digital electric signal. The frequency offset estimating apparatus comprises a phase offset calculating section, for calculating a phase offset in said base band digital electric signal; a phase offset change calculating section, for calculating a change of said phase offset, namely a phase offset change, in accordance with the phase offset calculated by said phase offset calculating section; an ambiguity deciding section, for deciding whether there is ambiguity in said phase offset change calculated by said phase offset change calculating section, and outputting the phase offset change having no ambiguity; and a loop filtering section, for acquiring a weighted average of the phase offset change outputted by said ambiguity deciding section.05-21-2009
20090116851Optical Receiver Having Bandwidth Control For Intersymbol Interference Compensation - Apparatus and techniques for receiving and processing an optical signal. In one implementation, an optical receiver is provided to include a delay line interferometer, an etalon, and a data estimator for estimating the data carried on a differentially modulated optical input signal. The delay line interferometer receives the input signal and issues differentially decoded constructive and destructive signals. The etalon filters the constructive signal with a transmission stopband imposed over the passband of the constructive signal. The bandwidth of the etalon stopband is selected based on the bandwidth of the modulation of the input signal in order to maximize received signal quality. The data estimator uses a difference between signals derived from the filtered constructive signal and the destructive signal for estimating data.05-07-2009
20110206385Method and Apparatus for Frame Detection and Polarization Separation - An optical receiver comprising a frame detector configured to receive a polarized signal comprising a first bit stream and a second bit stream, and further configured to identify a plurality of frames in the first bit stream and the second bit stream using a composite header, and a time-domain equalizer (TDEQ) configured to separate the first bit stream and the second bit stream using a portion of the composite header.08-25-2011
20090245815Apparatus and method for frequency offset monitoring used in digital coherent optical receiver - The present invention discloses a frequency offset detecting apparatus and method for use in a digital coherent optical receiver. The digital coherent optical receiver comprises: a front-end processing section for generating a digital baseband electric signal; an equalizer for performing equalized filtering on the digital baseband electric signal; and the frequency offset detecting apparatus for detecting frequency offset contained in the digital baseband electric signal or frequency offset contained in a signal outputted by the equalizer; wherein the frequency offset detecting apparatus comprises an argument difference obtaining unit, a first subtracter, a second subtracter, a quantizer and an averager, of which the argument difference obtaining unit obtains an argument difference of adjacent symbols in a signal inputted therein; the first subtracter subtracts an output of the averager from the argument difference obtained by the argument difference obtaining unit; the quantizer performs uniform quantization with predetermined intervals on an output of the first subtracter; the second subtracter subtracts an output of the quantizer from the argument difference obtained by the argument difference obtaining unit; and the averager averages an output of the second subtracter.10-01-2009
20090245816Filter coefficient changing apparatus and method - The present invention discloses filter coefficient changing apparatus and method for use in a dual-polarized optical coherent receiver. The apparatus comprises a controlling unit, a switching unit and a new coefficient obtaining unit. The switching unit is connected between a first filter coefficient updating unit and a first filtering unit and a second filtering unit; the new coefficient obtaining unit generates new filter coefficients for the first filtering unit and the second filtering unit in accordance with filter coefficients outputted by a second filter coefficient updating unit; and the controlling unit generates a control signal that controls switching of the switching unit. Upon reception of the control signal, the switching unit breaks off output of the filter coefficients from the first filter coefficient updating unit, transmits new filter coefficients from the new coefficient obtaining unit to the first filtering unit and the second filtering unit, and subsequently resumes the output of the filter coefficients from the first filter coefficient updating unit to the first filtering unit and the second filtering unit.10-01-2009
20090252505PHASE-MODULATED SIGNAL RECEIVING DEVICE - A monitor circuit detects the average light receiving current of a photoelectric conversion device for receiving a positive-phase intensity-modulated signal and outputs the detected current value to a control unit. The control unit adjusts the heater current of a phase adjustment heater in such a way as to maximize or minimize the output of the monitor circuit and controls the amount of delay of the phase reference light of a demodulator.10-08-2009
20090097866OPTICAL RECEIVING DEVICE AND OPTICAL TRANSMISSION SYSTEM - According to an aspect of an embodiment, an apparatus includes: a wavelength-to-transmission quality characteristic obtaining unit for obtaining a wavelength-to-transmission quality characteristic; a residual dispersion-to-transmission quality characteristic saving unit for saving a residual dispersion-to-transmission quality characteristic; a wavelength-to-residual dispersion characteristic generating unit for generating a wavelength-to-residual dispersion characteristic from a relationship between the wavelengths of the other channels and the residual dispersion based on the wavelength-to-transmission quality characteristic and the residual dispersion-to-transmission quality characteristic; a variable dispersion compensator for providing variable dispersion compensation to another channel,; and a variable dispersion compensation controlling unit for performing setting control on a dispersion compensation amount.04-16-2009
20100221021OPTICAL RECEIVER AND CONTROL APPARATUS - An optical receiver that can receive WDM signal light in which first and second wavelength bands are combined. Within optical reception units corresponding to each channel is respectively provided tunable dispersion compensator (TDC) modules in which one wavelength band is made a design standard. When known, based on signal light channel information (wavelength, frequency, channel number) notified from outside, that signal light of the second wavelength band is being input to the receiver, then in the TDC module that performed chromatic dispersion compensation of the signal light, control is performed to shift the center frequency of the dispersion compensation range by a predetermined amount corresponding to the wavelength of the signal light. When the signal light of the first wavelength band is input, shift control of the dispersion compensation range is not performed, and the dispersion compensation range at the time of designing is maintained. As a result, chromatic dispersion compensation of signal light of respective wavelength bands can be performed with high accuracy by one type of TDC.09-02-2010
20100239270Electronic Compensation of Nonlinear Effects of Semiconductor Optical Amplifiers - Systems and methods are disclosed for compensating for impairments caused by a semiconductor optical amplifier (SOA). One such method comprises receiving an optical signal which has been distorted in the physical domain by an SOA, and propagating the distorted optical signal backward in the electronic domain in a corresponding virtual SOA.09-23-2010
20130216240COHERENT LIGHT RECEIVING DEVICE, SYSTEM, AND METHOD - A coherent light receiving device includes a coherent receiving unit which mixes a received optical signal with local light and performs optical coherent detection to output a digital signal, a wavelength dispersion compensation unit which compensates for waveform distortion in the digital signal and outputs a digital signal after compensation, and a frequency difference detection unit which detects the frequency difference between the received optical signal and local light and notifies the wavelength dispersion compensation unit of the frequency difference, wherein the wavelength dispersion compensation unit performs compensation using a transfer function which is based on the frequency difference notified from the frequency difference detection unit and represents waveform distortion due to wavelength dispersion.08-22-2013
20100239269PHASE SYNCHRONIZATION APPARATUS AND DIGITAL COHERENT LIGHT RECEIVER - A phase synchronization method uses a removal path for removing an error component contained in an input signal and a delay addition path for adding a delay corresponding to a processing time period taken to remove the error component in the removal path. The removal path includes an averaging section. The averaging section includes a shift register and an obtaining unit. The shift register stores as many data as the maximum number of data to be averaged and successively receives processing data from which the error component has been extracted in the removal path. The obtaining unit obtains, among the successive processing data input to the shift register, as many processing data as the number of data to be averaged from a position near the center toward both ends in the shift register.09-23-2010
20110129235BURST-MODE OPTICAL SIGNAL RECEIVER - A burst-mode optical receiver is provided. The burst-mode optical receiver includes a preamplifier, a post-amplifier integrated into one body together with the preamplifier, and an operation controller for controlling operation of the preamplifier and the post-amplifier using an external reset signal input from a single external reset input terminal. As a result, it is possible to implement a burst-mode receiver for a gigabit-capable passive optical network (GPON) in which a preamplifier unit and a post-amplifier unit are integrated.06-02-2011
20090074428Reconstruction and restoration of two polarization components of an optical signal field - A digital version of both amplitude and phase of at least one generic polarization component of a received optical signal is developed using dual-polarization direct differential detection with digital signal processing. The received signal is split into orthogonal polarization components, each of which is split into three copies. For each orthogonal polarization component a) an intensity profile is conventionally obtained using a copy and b) phase information is obtained by supplying each remaining copy to a respective one of a pair of optical delay interferometers having orthogonal phase offsets, followed by respective balanced intensity detectors. The outputs the balanced intensity detectors and the intensity profiles are converted into digital representations and used to develop, via signal processing, the optical field information of at least one generic polarization component of the received optical signal. Compensation of impairments, such as PMD, is realized through further processing.03-19-2009
20090110409High sensitivity two-stage amplifier - The invention relates to amplifiers and in particular, to a transimpedance amplifier for high rate applications. Disclosed is a two stage transimpedance amplifier having a first stage comprising an amplifier and a load and a second stage comprising an amplifier and a resistor. Negative feedback is provided through a feedback resistor. Only two voltage conversions occur which reduces phase distortion, as compared to three stage transimpedance amplifiers which perform 3 voltage conversions.04-30-2009
20090052910Automatic dual receiver in a multi-wavelength fiber optic system - An optical-to-electrical converter may include and/or involve a splitter to separate one or more narrowcast signals from a broadcast signal, at least one broadcast signal receiver to receive the broadcast signal separated from one or more narrowcast signals, at least one narrowcast signal receiver to receive the narrowcast signal separated from the broadcast signal, the narrowcast receiver including an attenuator and a filter, and a controller including logic to dynamically monitor and adjust the attenuator to maintain separation between the broadcast and narrowcast signals.02-26-2009
20110129234Iterative Carrier Phase Compensation in Coherent Fiber Optic Receivers - A method and an optical receiver compensates for an error in a phase of an optical signal in a receiver. The signal includes blocks of symbols in a sequence. Each block is decoded based on a partially phase compensated symbols, and an average phase error for the block is estimated. Forward phase compensation and backward phase compensation is performed on the block based on the average phase error, and the decoding, estimating, performing is iterated until a termination condition is satisfied to produce a phase compensated block.06-02-2011
20090142077COHERENT OPTICAL DETECTION AND SIGNAL PROCESSING METHOD AND SYSTEM - A method and system of coherent detection of optical signals. The system utilizes a digital signal processor to recover an incoming optical signal. The system employs a local oscillator, which does not need to be phase locked to the signal. The signal may be consistently recovered, even when the polarization state varies over time. Additionally, the signal may be recovered when it comprises two channels of the same wavelength that are polarization multiplexed together. In addition, any impairment to the signal may be reversed or eliminated.06-04-2009
20090034989LIGHT SIGNAL PROCESSING DEVICE AND LIGHT SIGNAL STORING DEVICE - There is provided a light signal processing device. The light signal processing device includes a label recognition circuit and an electro-absorption optical switch. The label recognition circuit includes: a plurality of photodiodes coupled to each other in parallel; a resonant tunneling diode coupled in series with the photodiodes; and a data buffer coupled to a connection point between the photodiodes and the resonant tunneling diode. The label recognition circuit is adapted to latch an optical bit signal inputted into the photodiodes. The electro-absorption optical switch is driven directly by an output signal outputted from the label recognition circuit.02-05-2009
20100172658OPTICAL RECEIVER CIRCUIT - In the case in which an input voltage to a comparator COMP reaches (1/2)×Vcc from initial Vcc in accordance with lowering of the electric potential at a nodal point N07-08-2010
20110243576OPTICAL RECEIVER FOR THE WDM SYSTEM AND THE METHOD FOR CONTROLLING THE SAME - An optical receiver with a simplified arrangement able to compensate the optical loss of the transmission medium is disclosed. The optical receiver of the invention includes an SOA in the front end thereof, an optical de-multiplexer, and a plurality of receiver modules that receives de-multiplexed light. The optical gain of the SOA is adjusted based on the electrical signals output from respective optical modules. When the receiver modules show the output thereof in a preset range, the bias current is kept unchanged, while, one receiver module shows the output out of the range, the bias current is incremented or decremented. When one receiver module shows the output out of the absolute maximum/minimum, the bias current is forced to the initial value.10-06-2011
20110150506OPTICAL RECEIVER AND RECEIVING METHOD - An optical receiver includes an optical front-end, a digital converter, a frequency-characteristic-difference reducing unit and an identifying unit. The optical front-end splits an input signal light into signal light components on a basis of local light and converts the split signal light components into electrical signals. The digital converter converts the electrical signals, converted by the optical front end, into digital signals. The frequency-characteristic-difference reducing unit reduces a frequency-characteristic difference between the digital signals converted by the digital converter. The identifying unit identifies each of the digital signals whose frequency-characteristic difference is reduced by the frequency-characteristic-difference reducing unit.06-23-2011
20110249981COHERENT OPTICAL RECEIVER SYSTEMS AND METHODS - The present disclosure relates to coherent optical receiver systems and methods for determining and correcting for optical angle and magnitude imbalance and for delay imbalance between quadrature paths. The present invention iteratively determines and corrects imbalance error and differential delay entirely in the digital domain (after an analog to digital conversion) in the presence of all the other impairments (polarization mode dispersion, chromatic dispersion, polarization gain imbalance, and polarization delay imbalance) using only the corrupted received signal during normal operation, i.e. without the use of training data. The present invention provides an effective adaptive scheme to drive impairments to zero, without using of any calibration of training, and may be applied during normal operation of the receiver via electrical circuitry or the like.10-13-2011
20110076033COHERENT OPTICAL SYSTEM COMPRISING A TUNABLE LOCAL OSCILLATOR - A method and an optical network component for data processing in an optical network. A first signal and a second signal are influenced by a tunable element. The first signal is an incoming optical signal, and the second signal is a local oscillator signal generated by a laser. The laser has an optical gain element that is tuned by the tunable element. A communication system is provided with the optical network component.03-31-2011
20110255880IR RECEIVING UNIT - An IR receiver having a decision logic circuit for activating or deactivating a squelch. Activation or deactivation of the squelch is effected in dependence on a mean value of the frequency, a variance of the receiver intermediate frequency, a mean value of the audio amplitude, a variance of the audio amplitude and/or a signal strength of the receiver intermediate circuit frequency.10-20-2011
20110211847OPTICAL RECEIVER AND CLOCK GENERATION METHOD - An optical receiver includes a dispersion mitigator configured to mitigate a wavelength dispersion value in an optical signal by using a set dispersion value, a phase difference signal generator configured to generate a phase difference signal by calculating the phase difference between a first clock signal included in an optical signal mitigated by the dispersion mitigator, and a second clock signal, a dispersion value adjuster configured to adjust the set dispersion value set in the mitigator, a controller configured to control fluctuations appearing in a phase difference signal generated by the phase difference signal generator when the dispersion value is adjusted by the dispersion value adjuster, and a clock generator configured to generate the second clock follow up the phase of the first clock, being based on the phase difference signal controlled by the controller.09-01-2011
20080267638OPTICAL RECEIVER - An optical mixing part mixing a received optical signal and local oscillator light in at least two kinds of phases and extracting at least two-system optical signals corresponding to each light phase; a photoelectric conversion part converting the at least two-system optical signals obtained in the optical mixing part into electric analog signals; an analog-to-digital conversion part converting the electric analog signals into digital signals; and a control part processing the digital signals thereby detecting a light phase difference between the respective systems in the optical mixing part and supplying a signal for correcting the light phase between the systems to the optical mixing part to control the optical mixing part so that the light phase difference becomes to zero or close to a desired value when the light phase difference has a shift from the desired value.10-30-2008
20110255879Electronic Nonlinearity Compensation For Optical Transmission Systems - Embodiments for optical communication are provided in which a receiver includes a digital signal processor configured to process a digital form of an input signal. In one embodiment, the digital signal processor includes a first electronic chromatic dispersion compensation module for compensating the digital form of the input signal, at least one nonlinearity compensation stage for serially compensating an output of the electronic chromatic dispersion compensation module; and a second electronic chromatic dispersion compensation module for compensating an output of the at least one nonlinearity compensation stage.10-20-2011
20080205906PREAMPLIFIER AND OPTICAL RECEIVING APPARATUS USING THE SAME - When an optical signal that is a wide dynamic range and different in level depending on burst signals is input as in a GPON system, a preamplifier can stably control the gain within a short preamble. The gain changeover of the preamplifier is controlled by the aid of timing information that is extracted from a data signal as data count number, to change over the gain at a high speed and with high precision. A level detector, a preamble recovery, a counter, and a control circuit are disposed within the preamplifier in addition to a TIA main body. In order to suppress the band deterioration or the phase margin reduction which are attributable to the gain changeover, there is provided a bias terminal for conducting a current injection and a current drawing with respect to the signal amplification transistor of the TIA main body.08-28-2008
20110026941VARIABLE DISPERSION COMPENSATION DEVICE - A dispersion compensation device includes a variable dispersion compensator configured to subject an input optical signal to dispersion compensation, an optical receiver configured to convert an optical signal subjected to dispersion compensation into an electrical signal, recover a clock signal and a received data signal from the electrical signal, and output clock lock information indicating whether the clock signal is locked to the electrical signal, a signal processor configured to output bit error rate information on the received data signal, and a controller configured to variably control a dispersion compensation value of the variable dispersion compensator based on the bit error rate information and the clock lock information.02-03-2011
20100329698SIGNAL PROCESSING CIRCUIT, OPTICAL RECEIVER, DETECTOR AND METHOD FOR COMPENSATING FOR WAVEFORM DISTORTION - A signal processing circuit includes: a first compensator configured to compensate for waveform distortion corresponding to chromatic dispersion of a received optical signal by using digital electrical signals obtained by sampling analog electrical signals by using a sampling signal, the analog electrical signals being obtained by opto-electric conversion of multiple optical signals that include an intensity of the received optical signal and phase information thereon; and a chromatic dispersion compensation controller configured to control a compensation value for the chromatic dispersion in the first compensation from the digital electrical signals in which the chromatic dispersion has been compensated for on the basis of a detected phase offset between the sampling signal and a modulation frequency of the received optical signal.12-30-2010
20100329697DIGITAL COHERENT RECEIVING APPARATUS - A digital coherent receiving apparatus includes a first oscillator for outputting a local light signal of a fixed frequency, a hybrid unit mixing the local light signal with a light signal received by a receiver, a second oscillator for outputting a sampling signal of a sampling frequency, a converter for converting the mixed light signal into digital signal synchronizing with the sampling signal, a waveform adjuster for adjusting a waveform distortion of the converted digital signal, a phase adjustor for adjusting a phase of the digital signal adjusted by the waveform adjustor, a demodulator for demodulating the digital signal adjusted by the phase adjuster, and a phase detector for detecting a phase of the digital signal adjusted by the phase adjuster, and a control signal output unit for outputting a frequency control signal on the basis of the detected phase signal to the second oscillator.12-30-2010
20110135320TECHNIQUE FOR CALIBRATING AND CENTERING AN OPTICAL RECEIVER - A technique for calibrating an optical receiver is described. During this technique, a front-end circuit in the optical receiver receives an optical signal that corresponds to a sequence with alternating groups of symbol types that correspond to binary values, where durations of the groups of a given symbol type, which can correspond to a first binary value or a second binary value, progressively decrease during the sequence. Then, the output of the feedback circuit is adjusted based at least on the sequence. When the durations of groups corresponding to the first binary value and the second binary value reach their minimum values in the sequence, a calibration value corresponding to the output of the feedback circuit is stored for use during a normal operating mode of the optical receiver.06-09-2011
20110052216Electronic dispersion compensation within optical communications using reconstruction - Electronic dispersion compensation within optical communications using reconstruction. Within a communication system that includes any optical network portion, segment, or communication link, etc., that optical component/portion of the communication system is emulated within the electronic domain. For example, in a communication device having receiver functionality, deficiencies that may be incurred by the at least one optical portion of the communication system are compensated in the electronic domain of the communication device having the receiver functionality by employing reconstruction logic and/or circuitry therein. Multiple decision feedback equalizers (DFE) circuitries, implemented in the electronic domain, may be employed to provide feedback from different portions of the receiver functionality in accordance with performing compensation of optical incurred deficiencies (e.g., dispersion, non-linearity, inter-symbol interference (ISI), etc.). Within a communication device's receiver portion, equalization and compensation is performed in the electronic domain as adapted for high speed applications and higher order modulation schemes.03-03-2011
20110052215Blind Equalization Algorithms for Adaptive Polarization Recovery and PMD Compensation - A device and method are disclosed for blind equalization of an optical signal to implement adaptive polarization recovery, Polarization Mode Dispersion (PMD) compensation, and residual Chromatic Dispersion (CD) compensation in a digital coherent optical communication system.03-03-2011
20100215380RECEPTION DEVICE AND RECEPTION METHOD - A reception device includes at least a light receiving unit, a phase calculation unit, and a demodulation unit. The light receiving unit receives intensity-modulated light from a transmission device. The transmission device executes phase modulation to a bit stream as an object to be transmitted and emits the intensity-modulated light which has an intensity changing at a preset time cycle and a phase changing in response to the phase modulation, and the phase is maintained during M cycles. The phase calculation unit detects the intensity of the intensity-modulated light p times per cycle of the intensity-modulated light and repeatedly calculates the phase of the intensity-modulated light on the basis of a result of the detection. The demodulation unit executes demodulation, which corresponds to the phase modulation, to the phase calculated by the phase calculation unit, and generates transmitted bit stream.08-26-2010
20100166438OPTICAL INTERFEROMETER AND OPTICAL RECEIVER - An optical interferometer includes a substrate; a first and a second branch lines; a third and a fourth branch lines; a first interference portion for causing the first and the third branch lights to interfere with each other; and a second interference portion for causing the second and the fourth branch lights to interfere with each other; wherein each of the first and the third branch lines runs in the surface of the substrate such that the first and the third branch lines provide respective optical path lengths with a constant difference for a temperature change, and each of the second and the fourth branch lines runs in the surface such that the second and the fourth branch lines provide respective optical path lengths with a constant difference for a temperature change.07-01-2010
20100158541Optical communication apparatus and optical communication method - An optical communication apparatus includes a receiver configured to receive an optical signal transmitted from an optical transmitting apparatus; a detector configured to detect a predetermined pattern signal included in the optical signal; a calculator configured to calculate, based on a waveform of the predetermined pattern signal, an amount of dispersion of the predetermined pattern signal; and a compensator configured to compensate for dispersion according to the amount of dispersion.06-24-2010
20120121274Clock Recovery for Optical Transmission Systems - A receiver for an optical communications system which corrects distortion of a received signal. A clock recovery system utilising a feedback and feedforward system are provided. The feedback loop comprises a phase detector and a clock source, while the feedforward loop comprises the phase detector and a delay element for delaying the output of distortion correction system. The feedback loop has a significantly lower bandwidth than the feedforward path. There are also provided methods of optimising tap weights and of acquiring initial tap weights.05-17-2012
20110150505ZERO MEAN CARRIER RECOVERY - A method of data symbol recovery in a coherent receiver of an optical communications system. Two or more SYNC bursts, having a known symbol sequence and periodicity, are processed to derive an estimate of a frequency offset Δf between a transmit laser and a Local Oscillator (LO) of the receiver. A phase rotation κ(n) is computed based on the estimate of the frequency offset Δf, and applied to a plurality of data symbol estimates to generate corresponding rotated symbol estimates. The rotated symbol estimates are then filtered to generate corresponding decision values of each data symbol.06-23-2011
20110305464APPARATUS FOR COMPENSATING OPTICAL SIGNAL IMPAIRMENTS - Consistent with the present disclosure, a portion of light output from a laser, such as a local oscillator laser, is supplied to an optical circuit. The optical circuit may include a delay line interferometer that supplies a further optical signal that is sensed by a photodetector circuit. Alternatively, a 90 degree optical hybrid may be provided which receives two inputs whereby one input is delayed relative to the other input. The outputs of the optical hybrid are also supplied to a photodetector circuit. An electrical signal output from the photodetector circuit is indicative of changes in phase of the light output from the laser. A processor circuit may be configured to process the electrical signal to determine an accumulated phase of the laser light based on the electrical signal. Alternatively, based on the electrical signal, phase offset values may be obtained to offset or compensate local oscillator phase noise. In another example, the laser may be provided in an optical transmitter, and the electrical signal may be used to correct for undesired phase changes in a modulated optical signal. Further, the electrical signal may be provided to measure the phase noise for diagnostic or monitoring purposes.12-15-2011
20100172657OPTICAL RECEIVER WITH TRANS-IMPEDANCE RESPONDING IN BIT-BY-BIT TO INPUT SIGNAL - An optical receiver implemented with a pre-amplifier with an additional trans-impedance able to respond to the input signal in bit-by-bit is disclosed. The optical receiver provides a photodiode to convert an optical signal into a photocurrent, a trans-impedance amplifier to convert the photocurrent to a voltage signal, and an additional trans-impedance circuit able to respond instantaneously to the voltage signal. The additional trans-impedance includes a FET whose gate is fully fixedly biased and the source thereof receives the voltage signal. The FET may bypass the current flowing in the intrinsic trans-impedance instantaneously.07-08-2010
20120039618SELF-ADAPTIVE RECEIVERS NOT REQUIRING FEC FEEDBACK - Optical communications networks rely on optical receivers to demodulate optical signals and convert the demodulated optical signal into an electrical signal. Optical receivers may be associated with one or more characteristics which can be made to vary during a transmission of an optical signal in order to improve the quality of the received signal. The present invention may determine a value for the characteristics based on an amount of optical filtering on a communications link which transmits the signal. The value for the characteristics of the receiver may be determined by observing a characteristic of a detector associated with the receiver, such as a ratio of the average photocurrents of the constructive and destructive ports of the detector. The observed characteristic of the detector may be mapped to a predetermined value for the characteristic of the receiver in a lookup table, which may be queried during operation of the receiver.02-16-2012
20110064421APPARATUS AND METHOD FOR EQUALIZING CHROMATIC DISPERSION AND DIGITAL COHERENT OPTICAL RECEIVER - This application relates to an apparatus and a method for equalizing chromatic dispersion and a digital coherent optical receiver. The apparatus for equalizing chromatic dispersion comprising: a chromatic dispersion equalizing unit, for compensating chromatic dispersion of an input signal; and an additional time delay removing unit, for removing, in accordance with frequency offset of the input signal, chromatic dispersion equalization time delay generated by the chromatic dispersion equalizing unit.03-17-2011
20120002979Method And Apparatus For Polarization-Division-Multiplexed Optical Receivers - An optical receiver includes a two-stage constant modulus algorithm (CMA) equalizer. The first stage is a modified version of a CMA equalizer and the second stage is a conventional CMA equalizer. The first stage may be made up of four sub-equalizers, of which only two of the sub-equalizers are independent, i.e., uncorrelated to each other. This first stage equalizer compensates for polarization-mode dispersion (PMD). The second stage equalizer is a conventional CMA equalizer made up of four sub-equalizers that are adjusted independently. This second stage equalizer may compensate for polarization-dependent loss (PDL). The receiver includes a first processor that determines PMD information based on a plurality of transfer function parameters of the modified CMA equalization of the first stage equalizer and the modified-equalized output and a second processor that determines PDL based on a plurality of transfer function parameters of the CMA equalization of the second stage equalizer.01-05-2012
20130011144METHOD AND APPARATUS FOR NOISE CANCELLATION - Method and apparatus of denoising recurrent signals comprising: providing first and second noisy signals each comprising a deterministic signal and (different realizations of) white noise; selecting one of the noisy signals as an input signal and the other noisy signal as a desired signal; providing an estimate of the deterministic signal in the input signal; determining the error between the estimated deterministic signal and the desired signal; adjusting the estimate of the deterministic signal using the error and producing an adjusted estimate of the deterministic signal.01-10-2013
20120057883METHOD FOR DATA PROCESSING IN AN OPTICAL NETWORK COMPONENT AND OPTICAL NETWORK COMPONENT - A method for data processing in an optical network component includes filtering and optically equalizing an incoming optical signal and modulating the optically equalized signal. A corresponding optical network component is also provided.03-08-2012
20120155890COMPLEXITY REDUCED FEED FORWARD CARRIER RECOVERY METHODS FOR M-QAM MODULATION FORMATS - The present disclosure provides a method of carrier phase error removal associated with an optical communication signal. The method includes estimating and removing a first phase angle associated with an information signal using coarse phase recovery, the information symbol being associated with a digital signal, the digital signal representing the optical communication signal; estimating a carrier frequency offset between a receiver light source and a transmitter light source by using the estimated first phase angle, the carrier frequency offset being associated with the information signal; removing carrier phase error associated with the carrier frequency offset; and estimating and removing a second phase angle associated with the information signal, the estimated second phase angle being based on the estimated first phase angle and the estimated carrier frequency offset.06-21-2012
20100092185OPTICAL RECEIVER - An optical receiver for receiving a processing modulated optical signal, the optical receiver includes a variable dispersion compensator for receiving the optical signal and for compensating chromatic dispersion of the optical signal in accordance with a predetermined chromatic dispersion value; a demodulator including a delay interferometer for receiving the compensated optical signal and for changing a phase moderation information of the compensated optical signal into an amplitude moderation information, and an optical demodulator for changing the amplitude moderation information of the optical signal into an electrical signal; a data regenerator for extracting a clock from the electric signal and for regenerating data from the electric signal by the use of the clock; and a controller for setting an optical phase to the delay interferometer and for setting the dispersion compensation value to the variable dispersion compensator.04-15-2010
20100247113PHASE ERROR CORRECTION IN A COHERENT RECEIVER - A method and apparatus for correcting of phase errors in a coherent optical receiver are disclosed. Embodiments include a method for calculating a phase error between in-phase and quadrature-phase component signals, multiplying the phase error by one of the component signals and subtracting the result from the other component signal to output a corrected signal.09-30-2010
20120128377OPTICAL DIGITAL COHERENT RECEIVER - An ALC processing unit to adjust the signal level of outputs from an adaptive equalizer to a target value is provided in a stage later than the adaptive equalizer and earlier than a frequency offset estimation/compensation unit in an optical digital coherent receiver. The ALC processing unit generates a histogram that counts the number of samples for discrete monitored values corresponding to amplitude values of outputs from the adaptive equalizer, and determines a level adjustment coefficient that is to be multiplied by an output from the adaptive equalizer so as to multiply the determined coefficient by the output from the adaptive equalizer so that the monitored value of the peak value of the histogram is the target value.05-24-2012
20120128376PMD-insensitive method of chromatic dispersion estimation for a coherent receiver - Consistent with the present disclosure, a method and system for estimating chromatic dispersion of an optical signal in a coherent receiver is provided that is insensitive to polarization mode dispersion (PMD) and other polarization effects in the optical communication system. The effects of chromatic dispersion in the optical system are estimated by first calculating a phase shift between a pair of related frequency domain data outputs of a Fourier transform circuit. The calculated phase shift includes a linear phase component that is proportional to the chromatic dispersion, a DC constant phase component, and a data spectrum component. The calculated phase shift is then averaged over a number of clock cycles to remove the data spectrum components. The time averaged result is used to normalize any effects of PMD from the received signal. A slope of the linear phase component as a function of frequency is then calculated and used to estimate the value for chromatic dispersion. The chromatic dispersion estimate is then used to determine a number of coefficients of an inverse frequency response of the chromatic dispersion in the system, and is used to compensate for the chromatic dispersion.05-24-2012
20110182591OPTICAL RECEIVER - An optical receiver includes: an optical amplifier amplifying an optical signal fed thereinto according to an operating current fed thereinto, the optical signal being a wavelength-multiplexed optical signal, a demultiplexer demultiplexing an optical signal output from the optical amplifier; and an operating-current control circuit selecting a monitoring target from a plurality of wavelength signals output from the demultiplexer and controlling the operating current of the optical amplifier so that optical power of the monitoring target is controlled to be a predetermined value.07-28-2011
20120213532OPTICAL RECEIVER, SIGNAL PROCESSOR, AND OPTICAL RECEIVING METHOD - An optical receiver includes a splitter that splits a local oscillator lightwave into a first local oscillator lightwave and a second local oscillator lightwave; a measurement unit that measures phase variation of the first local oscillator lightwave; a receiving unit that receives a signal lightwave and the second local oscillator lightwave and mixes these lightwaves and converts the mixed lightwaves into digital signal; a dispersion compensator that reduces chromatic dispersion of the digital signal; a phase processing unit that rotates phase of the dispersion-reduced signal based on the phase variation; and a discriminating unit that discriminates the phase-rotated signal.08-23-2012
20120134685LOOP FILTER - A loop filter include: a register that stores a result of arithmetic operation performed on a complex signal and outputs the stored complex signal; a first multiplier that multiplies the complex signal output from the register and a predetermined coefficient; an absolute value judging unit that outputs a multiplier coefficient used to control such that the amplitude of the complex signal output from the register is held in a predetermined range; a multiplier that multiplies an output from the first multiplier and the multiplier coefficient; a second multiplier that multiplies an input signal and a value (1−the predetermined coefficient); and an adder that adds an output from the multiplier to an output from the second multiplier and inputs a result of addition into the register.05-31-2012
20120224868OPTICAL RECEIVER BASED ON A DECISION FEEDBACK EQUALIZER - An optical receiver, a method of operating an optical receiver, a correction based transimpedance amplifier circuit, and a method of adjusting an output of a transimpedance amplifier. In one embodiment, the optical receiver comprises an optical-to-electrical converter, a transimpedance amplifier, and a correction circuit. The optical-to-electrical converter is provided for receiving an optical signal and converting the optical signal to an electrical signal. The transimpedance amplifier is provided for receiving the electrical signal from the optical-to-electrical converter and for generating from the electrical signal an amplified electrical signal. The amplified electrical signal has inter symbol interference resulting from a reduced bandwidth of the transimpedance amplifier. The correction circuit is provided for receiving the amplified electrical signal from the transimpedance amplifier and for generating, from the amplified electrical signal, an output signal including corrections for the inter symbol interference in the amplified electrical signal effectively increasing a bandwidth of the optical receiver.09-06-2012
20080298816RECEIVER AND ELECTRONIC DEVICE - An abnormal pulse detection circuit in a receiver of the present invention includes: an incoming pulse edge detection circuit which detects the moment of rise of an input signal and outputs the result of the detection as an edge detection signal; a muting reference pulse generation circuit which generates a muting reference pulse based on the edge detection signal; a logic circuit which outputs a signal indicating a negative AND of the muting reference pulse and the input signal; a muting signal generation circuit which generates a muting signal from the output signal of the logic circuit; and a switching circuit which outputs the input signal or the muting signal. The receiver of the present invention can therefore reduce discomfort in hearing reproduced sound in case where a noise occurs in an audio signal due to a variation in pulse width.12-04-2008
20110229153OPTICAL RECEIVER - In an optical receiver of a long-haul high-speed WDM/OADM system, a control technique is provided that can accurately control a variable dispersion compensator with an inexpensive configuration even under strict SNR conditions. Signal reception characteristic data (a bit error rate, a clock extraction result, and a frame synchronization result) is obtained and an optimum dispersion compensation amount of the dispersion compensator is calculated. The signal reception characteristic data is saturated by a high SNR. In the case where desired dispersion control accuracy cannot be obtained, an input level of a photodiode is reduced by controlling an output level of an amplifier or a variable optical attenuator. Further, in a state in which a received SNR is deteriorated, the signal reception characteristic data is obtained and the optimum dispersion compensation amount of the dispersion compensator is calculated again.09-22-2011
20120087680METHOD FOR CARRIER FREQUENCY RECOVERY AND OPTICAL INTRADYNE COHERENT RECEIVER - A method for carrier frequency recovery in an optical coherent transmission system is provided in which at least one kind of equalization of a received signal is performed in frequency domain, the method comprising: performing a frequency offset compensation in frequency domain on a received signal according to an estimated value of the frequency offset; obtaining the signal with the frequency offset compensated. Further, an optical coherent receiver is provided comprising: an equalization unit, adapted to perform at least one kind of optical distortion compensation of a received signal in frequency domain; a frequency offset compensation unit, adapted to perform the frequency offset compensation in frequency domain on a received signal according to an estimated value of the frequency offset to obtain the signal with frequency offset compensated.04-12-2012
20120087679CARRIER PHASE ESTIMATION FILTER LENGTH OPTIMIZATION - The present disclosure provides a system, apparatus and method to reduce phase noise associated with a received data signal, while optimizing system performance. An optimal length of a digital filter, employed in a carrier phase recovery process, is determined such that phase noise is reduced in the received data signal. Reduction of the phase noise present in the received data signal leads to improved receiver performance. The optimal length of the digital filter may be continuously performed, resulting in optimal performance of the receiver.04-12-2012
20120148265COHERENT OPTICAL RECEIVING DEVICE CAPABLE OF DIGITAL EQUALIZATION OF OPTICAL INPUT, DIGITAL EQUALIZATION METHOD FOR OPTICAL INPUT AND COHERENT OPTICAL TRANSMITTING/RECEIVING DEVICE - A coherent optical receiving device capable of digital equalization of an optical input, and a method thereof. The coherent optical receiving device includes a chromatic dispersion compensating unit configured to comprise a filter for chromatic dispersion compensation and compensate for chromatic dispersion with respect to a digital signal that corresponds to an optical input using the filter; a decoder configured to generate a bit sequence of the signal which has been compensated for chromatic dispersion; a bit error calculating unit configured to calculate a bit error amount in the bit sequence; and a controller configured to monitor the bit error amount, determine a filter coefficient that makes the bit error amount a minimum, and set the determined filter coefficient in the chromatic dispersion compensating unit.06-14-2012
20110158658Optical Subchannel-Based Cyclical Filter Architecture - The present invention includes novel techniques, apparatus, and systems for optical WDM communications. Tunable lasers are employed to generate respective subcarrier frequencies which represent subchannels of an ITU channel to which client signals can be mapped. In one embodiment, subchannels are polarization interleaved to reduce crosstalk. In another embodiment, polarization multiplexing is used to increase the spectral density. Client circuits can be divided and combined with one another before being mapped, independent of one another, to individual subchannels within and across ITU channels. A crosspoint switch can be used to control the client to subchannel mapping, thereby enabling subchannel protection switching and hitless wavelength switching. Network architectures and subchannel transponders, muxponders and crossponders are disclosed, and techniques are employed (at the subchannel level/layer), to facilitate the desired optical routing, switching, concatenation and protection of the client circuits mapped to these subchannels across the nodes of a WDM network.06-30-2011
20080253777Compensating For Data Degradation - The present invention relates to a communication system having a central station and a plurality of outstations. The central station is configured to execute a compensation procedure for compensating for degradation of data from the outstations, the compensation procedure having a plurality of adjustable characteristics, which characteristics are governed by a parameter set. The central station stores a respective parameter set in respect of each outstation; and, for each outstation, applies the compensation algorithm to data from that outstation using the parameter set associated with that outstation. In an initialization phase, the central station tests a plurality of starting parameter sets on data from a given outstation and selects the set providing the best compensation. The selected set is stored for subsequent compensation of data from that outstation.10-16-2008
20100086315OPTICAL RECEIVER ABLE TO PREVENT LOS ALARM FROM MALFUNCTIONING - An optical receiver able to generate the LOS alarm reliably is disclosed. The optical receiver module in the optical receiver provides a level monitor that monitors the average of the optical input, compares it with a reference and generates a decision signal that is provided to the squelching unit. The squelching unit, by receiving the decision signal, isolates the outputs of the output buffer from the inputs thereof and fixes the outputs of the receiver module in the level “0” or the level “1”. Even the main amplifier is coupled with the receiver optical module in the AC mode; no complicated response appears in the input of the main amplifier.04-08-2010
20130170842Method and System for Equalization and Decoding Received Signals Based on High-Order Statistics in Optical Communication Networks - A method equalizes and decodes a received signal including a sequence of symbols. Subsequences of the signal are selected, wherein the subsequences are overlapping and time shifted. For each subsequence, statistics of the channel corresponding to a pattern in the subsequence are selected, wherein the statistics include high-order statistics. A transmitted signal corresponding to the received signal is then estimated based on the statistics.07-04-2013
20110274442PILOT SYMBOL AIDED CARRIER PHASE ESTIMATION - Methods and systems for processing an optical signal in a communication system are disclosed. The disclosed methods yield benefits for estimation and tracking of carrier phase of received signals at a digital coherent receiver. Specifically, phase ambiguity is removed by the insertion of pilot symbols into a transmitted data stream. Pilot symbols are detected from a received signal, and carrier phase is estimated for the detected pilot symbols. If carrier phase track of received data symbols was lost, a correction is applied to recover the track. Coherent symbol decoding may be used which has not been possible with prior art techniques due to the possibility of phase tracking loss.11-10-2011
20090148171DQPSK/DPSK OPTICAL RECEIVER WITH TUNABLE OPTICAL FIBERS - An optical receiver includes a first interferometer having a plurality of arms. The optical receiver further includes first tunable optical filters connected in series with the arms of the first interferometer, where each first tunable optical filter is tuned to filter a region of overlap in the optical frequency spectrum between adjacent optical channels.06-11-2009
20130101300POWER ADJUSTMENT OF IN-PHASE AND QUADRATURE COMPONENTS AT A COHERENT OPTICAL RECEIVER - It is disclosed an optical coherent receiver for an optical communication network. The optical coherent receiver is configured to receive a modulated optical signal and to process it for generating an in-phase component and a quadrature component. The optical coherent receiver comprises a power adjuster in turn comprising a multiplying unit and a retroactively connected digital circuit. The multiplying unit is configured to multiply the in-phase and quadrature components by in-phase and quadrature gains, respectively, thereby providing power-adjusted in-phase and quadrature components. The digital circuit is configured to compute: a common gain indicative of a sum of the powers of the power-adjusted in-phase and quadrature components; a differential gain indicative of a difference between the powers of the power-adjusted in-phase and quadrature components; and the in-phase and quadrature gains as a product and a ratio, respectively, between the common gain and the differential gain.04-25-2013
20090317094Maximum Likelihood Sequence Estimation in Optical Fibre Communication Systems - A method of and a receiver(12-24-2009
20080199192Optical Receiver - A receiver for a differentially phase shift keying formatted optical signal, such as an RZ-DPSK formatted optical signal. Dither control loops are provided for controlling path length in a demodulator and/or for controlling the center wavelength of an optical band pass filter. A feedback loop is provided for controlling the gain of a pre-amplifier, and a method of protecting against optical transients by disabling a pre-amplifier is also provided. A preset delay may be provided to compensate for the differential delay in paths associated with the demodulator arms. When the signal is an RZ-DPSK modulated signal, a clock for retiming data from the optical signal may be derived from a signal on the data path.08-21-2008
20080199191MAXIMUM LIKELIHOOD SEQUENCE ESTIMATION FOR HIGH SPECTRAL EFFICIENCY OPTICAL COMMUNICATION SYSTEMS - Severe inter-symbol interference (ISI), introduced by narrow-band optical filtering in high spectral efficiency wavelength-division multiplexed (WDM) systems to avoid coherent WDM crosstalk, can be substantially mitigated by the use of maximum-likelihood sequence estimation (MLSE) reception. Compared to conventional threshold detection, the use of an MLSE receiver allows, for example, a 22% reduction in optical receive filter bandwidth. For tight optical filtering, the MLSE receiver benefits from taking into account noise correlation. MLSE receivers with one and with two samples per bit are described and it is shown that while oversampling is beneficial for wide-band optical filters, the benefit goes away for narrow-band optical filtering, thereby facilitating MLSE design for rates beyond 10 Gb/s.08-21-2008
20100316394Optical receiver and jitter tolerance control method - An optical receiver includes an optical device that receives input light and converts the input light to an electric signal; an equivalent part that carries out waveform shaping on the electric signal; an amplifier that amplifies the electric signal; a discrimination part that discriminates data of the electric signal; an input optical power detecting part that detects input optical power of the input light; and a control part that makes an error rate in the electric signal with respect to the input optical power worse when the input optical power detected by the input optical power detecting part is equal to or less than a value corresponding to minimum receiver sensitivity.12-16-2010
20120281992SYSTEMS AND METHODS FOR OPTICAL RECEIVER DECISION THRESHOLD OPTIMIZATION - The present invention provides systems and methods for a receiver threshold optimization loop to provide self-contained automatic adjustment in a compact module, such as a pluggable optical transceiver. The receiver threshold optimization loop utilizes a performance metric associated with the receiver, such as FEC, to optimize performance of the receiver. The receiver is optimized through a change in the receiver threshold responsive to the performance metric. Advantageously, the present invention provides improved receiver performance through a continuous adjustment that is self-contained within the receiver, such as within a pluggable optical transceiver compliant to a multi-source agreement (MSA). The receiver threshold optimization loop can include a fine and a coarse sweep of adjustment from an initial setting.11-08-2012
20120281991OPTICAL RECEIVER COMPENSATING INPUT OFFSET - A differential amplifier capable of canceling an input offset current and expanding a linearly operating range is disclosed. The differential amplifier, which is preferably applicable to an optical receiver to convert a photocurrent into a voltage signal, includes a trans-impedance amplifier and an offset canceller that detects output offset and extracts input current to cancel the output offset. Moreover, the extracted input current traces the average level of the input voltage to widen the linearly operating range of the trans-impedance amplifier.11-08-2012

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